Six weeks of drug therapy were compared to six weeks of chiropractic adjustments. The drug therapy was considered slightly more effective than chiropractic however 82% of the patients had side effects which included drowsiness, weight gain and dry mouth. Cardiac problems and glaucoma were also associated with amitriptyline use. Chiropractic patients had no side effects (apart from slight neck stiffness in the first two weeks of the study that 5% of the patients reported). After four weeks, chiropractic and drug therapy was halted in both groups. The patients who used drugs began having headaches again while the chiropractic group continued to express headache relief, as well as higher levels of energy and vitality than the drug therapy group.
Boline PD, Kasaak K, Bronfort G, Nelson C, Anderson AV, J Manipulative Physiol Ther. 1995 (Mar-Apr); 18 (3): 148-154